Something stronger than IncoherentInstances needed (Univalent Classes?)

Joachim Breitner mail at
Sat Jul 27 12:25:01 CEST 2013


Am Freitag, den 26.07.2013, 23:16 +0000 schrieb Simon Peyton-Jones:
> There is something odd about this. "IncoherentInstances" is meant to
> say "I don't care which path you take to proving this constraint".  So
> if we have
> 	instance C Int a
> 	instance C b Int
> and we try to solve (C Int Int) we should arbitrarily pick either.
> But we don't. 
> So I rather think that IncoherentInstances should be modified so it
> really does what it says.

I thought about this as well, but after reading the docs (which document
what is happing right now) it seemed to me that this behavior was
intentional. But if it is ok to liberate the meaning of
IncoherentInstances, even better. I’ll put it on my TODO list for NT

Joachim “nomeata” Breitner
  mail at joachim-breitner.de
  Jabber: nomeata at  • GPG-Key: 0x4743206C
  Debian Developer: nomeata at
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